Im trying to make a application that saves data on a website, to be persistent even if the user switches phone or have to uninstall the app temporarily. It seems as if it would be a good idea to extract the gmail from the phone, since for example the IMEI will change if the user switches phone. Is this possible? If not, is there any way to extract some unique information from the SIM-card?

edit: ok, this is how to find serial number of SIM-card:((TelephonyManager)this.getSystemService(Context.TELEPHONY_SERVICE)).getSimSerialNumber();But I would prefere the mail... any suggestions?